Real-World- Running.txt

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Vertical Ground Reaction Force

*speed up*

To create a larger vertical ground reaction force you must run on the hardest surface available

Coefficient of Friction

*speed up*

To create a larger coefficient of friction, the bottom surface of the shoes that you are wearing must have two characteristics:

(1) the material of the soles must be soft

(2) the surface of the soles must be rough

Muscle Force

To create a larger muscle force, three factors that influence the size of the muscle force must be considered:

(1) Muscle Size

-a muscle with a larger physiological cross-sectional area will create more muscle force

-increase via resistance training

(2) Muscle Length

-muscles stretched to 120% of their natural resting length generate the most muscle force

(3) Speed of the Muscle Contraction

-muscles that are concentrically contracted at slower speeds generate greater force than muscles that are concentrically contracted at faster speeds

Muscles Involved in Running

ANKLE PLANTAR FLEXION

Fibularis Brevis/Longus

Gastrocnemius

Plantaris

Soleus

Tibialis Posterior

KNEE EXTENSION

Gluteus Maximus

Rectus Femoris

TFL

Vastus Lateralis/Intermedius/Medialis

HIP EXTENSION

Adductor Magnus

Gluteus Maximus/Medialis/Minimus

Biceps Femoris

Semimembranosus

Semitendinosus

Moment Arm

The distance from the joint's axis of rotation to the line of pull of the muscle force.

To increase the moment arm distance, you would need to move the line of pull of the muscle force further away from the joint's axis of rotation.

One method for moving the line of pull of the muscle force would be to change the locations of the origin and insertion points for the muscle. It would be unethical to perform this type of surgery.

The only way we can change the moment arm distance is by changing the angle of the joint. When the long axes of the two bones connected at a joint are aligned long axis to long axis (straight line), the moment arm distance is the smallest.

Mass

*speed up*

SHORT-TERM

(1) wear the lightest clothing possible

(2) wear the lightest shoes possible

LONG-TERM

(1) lose fat mass

Radius of Resistance

The distance from the joint's axis of rotation to the center of mass of the body component.

Individuals with shorter bones will have shorter radii of resistance. There is nothing we can do to decrease bone length.

We can change the radius of resistance by changing the angles of the joints within the body component being rotated. We can decrease the radius of resistance by rotating the body component closer to the joint axis of rotation.

Application Time of Each Joint Torque

To increase the application time of the concentric ankle plantar flexion joint torque:

DURING THE PREP PHASE

the ankle must be dorsiflexed

DURING THE EXECUTION PHASE

a concentric ankle plantar flexion joint torque is applied until the ankle is maximally plantar flexed

To increase the application time of the concentric knee extension joint torque:

DURING THE PREP PHASE

the knee must be flexed

DURING THE EXECUTION PHASE

a concentric knee extension joint torque is applied until the knee is maximally extended

To increase the application time of the concentric hip extension joint torque:

DURING THE PREP PHASE

the hip must be flexed

DURING THE EXECUTION PHASE

a concentric hip extension joint torque is applied until the hip is maximally extended

Radius of Rotation

The distance from the joint's axis of rotation to the point of interest on the body component.

Individuals with longer bones will have longer radii of resistance. There is nothing we can do to increase bone length.

We can change the radius of rotation by changing the angles of the joints within the body component being rotated. Any change in a joint angle that rotates a portion of the body component farther from the axis of rotation will lengthen the radius of rotation.

Fluid Density

There are three atmospheric conditions that would reduce fluid density:

(1) higher altitude

(2) lower humidity

(3) warmer temperatures

Coefficient of Drag

A measure of the surface friction between the surface of the runner and the air as the runner moves through the air.

The coefficient of drag may be reduced by making the surface of the runner smoother.

This can be accomplished in 3 ways:

(1) any clothes that are worn must be made of materials that are extremely smooth

(2) worn clothes must be tight-fitting

(3) uncovered areas of the body should have the body hair removed

Area of Drag

A measure of the area of turbulent air behind the runner as the runner moves through the air.

The area of drag may be reduced by making the area of turbulent air behind the runner smaller.

There are 2 primary mechanisms for reducing the area of turbulent air behind the runner:

(1) make the area of the runner that collides with the air smaller

(2) have the runner run in an aerodynamic position

Unfortunately, neither of these 2 mechanisms can be implemented during running.

The primary method for making the area that collides with the air smaller is to reduce the height and weight of the runner. Doing either of these would affect the speeding up side of the model.

For these reasons, nothing can be done to reduce the area of drag during running.

Relative Velocity

A measure of the speed and direction of the air that is colliding with your body.

There are two approaches to reducing relative velocity.

(1) run on days when there is little or no wind

(2) use a movement technique called "drafting"

-following runner experiences a smaller drag force

-less energy expenditure (can lead to finishing race with a short duration sprint around lead runner)

Vertical Ground Reaction Force

*slow down*

There are 2 methods for reducing the magnitude of the vertical ground reaction force on the slowing down side of the model.

(1) create a smaller body component mass

SHORT-TERM

-wearing the lightest clothing and shoes possible

LONG-TERM

-changing body composition/loss of fat mass

(2) increase the application time of the vertical ground reaction force when the body collides with the ground

Coefficient of Friction

*slow down*

Decreasing the coefficient of friction is not an option because it will have no affect on the magnitude of the friction force slowing you down until you reduce it to a level that would allow the shoe to slip.

Application Time of Each External Force

The most effective method to decrease the application time of the friction force is to land with your foot underneath your center of mass.

4 real-world actions must be performed in order to increase the application time of the external forces slowing the body down:

(1) initial contact must be on the forefoot

(2) the ankle joint should be slightly plantar flexed prior to contact with the ground and then upon contact with the ground, the ankle plantar flexor muscles should be contracted to create an eccentric ankle dorsiflexion torque

(3) the knee joint should be slightly flexed prior to contact with the ground

(4) the hip joint should be slightly flexed prior to contact with the ground

for the drag force, there is nothing that can be done to reduce the application time

Mass

*slow down*

Theoretically, increasing the mass would be an effective method to reduce how much you slow down. Unfortunately, a larger mass is more difficult to move quickly.

There is a mass concept box on the speeding up side of the model; and the interpretation for that box was that the mass must be small if we want to effectively speed the body up. These two interpretations conflict.

However, the logic should be easy to see. We need to get the body moving quickly each time we propel ourselves forward. This requires the mass be as small as we can make it. There is no way to simultaneously increase the mass so that we don't slow down as much.

Distance

if you are planning to run for a 5K race, then only run 5000 meters. Do not run 5001, 5010, or 5020 meters. How is this accomplished?